Pathogenesis: A History of the World in Eight Plagues

by Jonathan Kennedy

If we trace the Tree of Life to the base of its trunk, we find the Last Universal Common Ancestor (LUCA): a single-celled, bacterium-like organism that is the distant progenitor of all living things, humans included.

It is therefore not the strongest or most intelligent members of our species who were most likely to survive long enough to pass on their DNA to the next generation; rather, it was humans who had the most effective immune system to cope with the onslaught of infectious diseases, or those who had mutations that made their cells unusable to microbes. Lots of these mutations not only conferred resistance to pathogens but also had a negative impact on cell function. This suggests that humans’ struggle for existence was a fight against microbes rather than alpha males and apex predators.

The Aedes aegypti mosquito that spreads yellow fever also benefited greatly from recent human activity because it likes to reproduce in containers full of stagnant water. This had led the American historian John McNeill to suggest that they are, in fact, a domesticated insect.

radix malorum est cupiditas, greed is the root of all evil.